/*
 * Copyright (C) 2011 Red Hat, Inc.
 *
 * This file is released under the GPL.
 */

#include "dm-space-map.h"
#include "dm-space-map-common.h"
#include "dm-space-map-metadata.h"

#include <linux/list.h>
#include <linux/slab.h>
#include <linux/device-mapper.h>

#define DM_MSG_PREFIX "space map metadata"

/*----------------------------------------------------------------*/

/*
 * An edge triggered threshold.
 */
struct threshold {
        bool threshold_set;
        bool value_set;
        dm_block_t threshold;
        dm_block_t current_value;
        dm_sm_threshold_fn fn;
        void *context;
};

static void threshold_init(struct threshold *t)
{
        t->threshold_set = false;
        t->value_set = false;
}

static void set_threshold(struct threshold *t, dm_block_t value,
                          dm_sm_threshold_fn fn, void *context)
{
        t->threshold_set = true;
        t->threshold = value;
        t->fn = fn;
        t->context = context;
}

static bool below_threshold(struct threshold *t, dm_block_t value)
{
        return t->threshold_set && value <= t->threshold;
}

static bool threshold_already_triggered(struct threshold *t)
{
        return t->value_set && below_threshold(t, t->current_value);
}

static void check_threshold(struct threshold *t, dm_block_t value)
{
        if (below_threshold(t, value) &&
            !threshold_already_triggered(t))
                t->fn(t->context);

        t->value_set = true;
        t->current_value = value;
}

/*----------------------------------------------------------------*/

/*
 * Space map interface.
 *
 * The low level disk format is written using the standard btree and
 * transaction manager.  This means that performing disk operations may
 * cause us to recurse into the space map in order to allocate new blocks.
 * For this reason we have a pool of pre-allocated blocks large enough to
 * service any metadata_ll_disk operation.
 */

/*
 * FIXME: we should calculate this based on the size of the device.
 * Only the metadata space map needs this functionality.
 */
#define MAX_RECURSIVE_ALLOCATIONS 1024

enum block_op_type {
        BOP_INC,
        BOP_DEC
};

struct block_op {
        enum block_op_type type;
        dm_block_t block;
};

struct bop_ring_buffer {
        unsigned begin;
        unsigned end;
        struct block_op bops[MAX_RECURSIVE_ALLOCATIONS + 1];
};

static void brb_init(struct bop_ring_buffer *brb)
{
        brb->begin = 0;
        brb->end = 0;
}

static bool brb_empty(struct bop_ring_buffer *brb)
{
        return brb->begin == brb->end;
}

static unsigned brb_next(struct bop_ring_buffer *brb, unsigned old)
{
        unsigned r = old + 1;
        return (r >= (sizeof(brb->bops) / sizeof(*brb->bops))) ? 0 : r;
}

static int brb_push(struct bop_ring_buffer *brb,
                    enum block_op_type type, dm_block_t b)
{
        struct block_op *bop;
        unsigned next = brb_next(brb, brb->end);

        /*
         * We don't allow the last bop to be filled, this way we can
         * differentiate between full and empty.
         */
        if (next == brb->begin)
                return -ENOMEM;

        bop = brb->bops + brb->end;
        bop->type = type;
        bop->block = b;

        brb->end = next;

        return 0;
}

static int brb_pop(struct bop_ring_buffer *brb, struct block_op *result)
{
        struct block_op *bop;

        if (brb_empty(brb))
                return -ENODATA;

        bop = brb->bops + brb->begin;
        result->type = bop->type;
        result->block = bop->block;

        brb->begin = brb_next(brb, brb->begin);

        return 0;
}

/*----------------------------------------------------------------*/

struct sm_metadata {
        struct dm_space_map sm;

        struct ll_disk ll;
        struct ll_disk old_ll;

        dm_block_t begin;

        unsigned recursion_count;
        unsigned allocated_this_transaction;
        struct bop_ring_buffer uncommitted;

        struct threshold threshold;
};

static int add_bop(struct sm_metadata *smm, enum block_op_type type, dm_block_t b)
{
        int r = brb_push(&smm->uncommitted, type, b);

        if (r) {
                DMERR("too many recursive allocations");
                return -ENOMEM;
        }

        return 0;
}

static int commit_bop(struct sm_metadata *smm, struct block_op *op)
{
        int r = 0;
        enum allocation_event ev;

        switch (op->type) {
        case BOP_INC:
                r = sm_ll_inc(&smm->ll, op->block, &ev);
                break;

        case BOP_DEC:
                r = sm_ll_dec(&smm->ll, op->block, &ev);
                break;
        }

        return r;
}

static void in(struct sm_metadata *smm)
{
        smm->recursion_count++;
}

static int out(struct sm_metadata *smm)
{
        int r = 0;

        /*
         * If we're not recursing then very bad things are happening.
         */
        if (!smm->recursion_count) {
                DMERR("lost track of recursion depth");
                return -ENOMEM;
        }

        if (smm->recursion_count == 1) {
                while (!brb_empty(&smm->uncommitted)) {
                        struct block_op bop;

                        r = brb_pop(&smm->uncommitted, &bop);
                        if (r) {
                                DMERR("bug in bop ring buffer");
                                break;
                        }

                        r = commit_bop(smm, &bop);
                        if (r)
                                break;
                }
        }

        smm->recursion_count--;

        return r;
}

/*
 * When using the out() function above, we often want to combine an error
 * code for the operation run in the recursive context with that from
 * out().
 */
static int combine_errors(int r1, int r2)
{
        return r1 ? r1 : r2;
}

static int recursing(struct sm_metadata *smm)
{
        return smm->recursion_count;
}

static void sm_metadata_destroy(struct dm_space_map *sm)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        kfree(smm);
}

static int sm_metadata_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        *count = smm->ll.nr_blocks;

        return 0;
}

static int sm_metadata_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        *count = smm->old_ll.nr_blocks - smm->old_ll.nr_allocated -
                 smm->allocated_this_transaction;

        return 0;
}

static int sm_metadata_get_count(struct dm_space_map *sm, dm_block_t b,
                                 uint32_t *result)
{
        int r;
        unsigned i;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
        unsigned adjustment = 0;

        /*
         * We may have some uncommitted adjustments to add.  This list
         * should always be really short.
         */
        for (i = smm->uncommitted.begin;
             i != smm->uncommitted.end;
             i = brb_next(&smm->uncommitted, i)) {
                struct block_op *op = smm->uncommitted.bops + i;

                if (op->block != b)
                        continue;

                switch (op->type) {
                case BOP_INC:
                        adjustment++;
                        break;

                case BOP_DEC:
                        adjustment--;
                        break;
                }
        }

        r = sm_ll_lookup(&smm->ll, b, result);
        if (r)
                return r;

        *result += adjustment;

        return 0;
}

static int sm_metadata_count_is_more_than_one(struct dm_space_map *sm,
                                              dm_block_t b, int *result)
{
        int r, adjustment = 0;
        unsigned i;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
        uint32_t rc;

        /*
         * We may have some uncommitted adjustments to add.  This list
         * should always be really short.
         */
        for (i = smm->uncommitted.begin;
             i != smm->uncommitted.end;
             i = brb_next(&smm->uncommitted, i)) {

                struct block_op *op = smm->uncommitted.bops + i;

                if (op->block != b)
                        continue;

                switch (op->type) {
                case BOP_INC:
                        adjustment++;
                        break;

                case BOP_DEC:
                        adjustment--;
                        break;
                }
        }

        if (adjustment > 1) {
                *result = 1;
                return 0;
        }

        r = sm_ll_lookup_bitmap(&smm->ll, b, &rc);
        if (r)
                return r;

        if (rc == 3)
                /*
                 * We err on the side of caution, and always return true.
                 */
                *result = 1;
        else
                *result = rc + adjustment > 1;

        return 0;
}

static int sm_metadata_set_count(struct dm_space_map *sm, dm_block_t b,
                                 uint32_t count)
{
        int r, r2;
        enum allocation_event ev;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        if (smm->recursion_count) {
                DMERR("cannot recurse set_count()");
                return -EINVAL;
        }

        in(smm);
        r = sm_ll_insert(&smm->ll, b, count, &ev);
        r2 = out(smm);

        return combine_errors(r, r2);
}

static int sm_metadata_inc_block(struct dm_space_map *sm, dm_block_t b)
{
        int r, r2 = 0;
        enum allocation_event ev;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        if (recursing(smm))
                r = add_bop(smm, BOP_INC, b);
        else {
                in(smm);
                r = sm_ll_inc(&smm->ll, b, &ev);
                r2 = out(smm);
        }

        return combine_errors(r, r2);
}

static int sm_metadata_dec_block(struct dm_space_map *sm, dm_block_t b)
{
        int r, r2 = 0;
        enum allocation_event ev;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        if (recursing(smm))
                r = add_bop(smm, BOP_DEC, b);
        else {
                in(smm);
                r = sm_ll_dec(&smm->ll, b, &ev);
                r2 = out(smm);
        }

        return combine_errors(r, r2);
}

static int sm_metadata_new_block_(struct dm_space_map *sm, dm_block_t *b)
{
        int r, r2 = 0;
        enum allocation_event ev;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        r = sm_ll_find_free_block(&smm->old_ll, smm->begin, smm->old_ll.nr_blocks, b);
        if (r)
                return r;

        smm->begin = *b + 1;

        if (recursing(smm))
                r = add_bop(smm, BOP_INC, *b);
        else {
                in(smm);
                r = sm_ll_inc(&smm->ll, *b, &ev);
                r2 = out(smm);
        }

        if (!r)
                smm->allocated_this_transaction++;

        return combine_errors(r, r2);
}

static int sm_metadata_new_block(struct dm_space_map *sm, dm_block_t *b)
{
        dm_block_t count;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        int r = sm_metadata_new_block_(sm, b);
        if (r) {
                DMERR_LIMIT("unable to allocate new metadata block");
                return r;
        }

        r = sm_metadata_get_nr_free(sm, &count);
        if (r) {
                DMERR_LIMIT("couldn't get free block count");
                return r;
        }

        check_threshold(&smm->threshold, count);

        return r;
}

static int sm_metadata_commit(struct dm_space_map *sm)
{
        int r;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        r = sm_ll_commit(&smm->ll);
        if (r)
                return r;

        memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
        smm->begin = 0;
        smm->allocated_this_transaction = 0;

        return 0;
}

static int sm_metadata_register_threshold_callback(struct dm_space_map *sm,
                                                   dm_block_t threshold,
                                                   dm_sm_threshold_fn fn,
                                                   void *context)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        set_threshold(&smm->threshold, threshold, fn, context);

        return 0;
}

static int sm_metadata_root_size(struct dm_space_map *sm, size_t *result)
{
        *result = sizeof(struct disk_sm_root);

        return 0;
}

static int sm_metadata_copy_root(struct dm_space_map *sm, void *where_le, size_t max)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
        struct disk_sm_root root_le;

        root_le.nr_blocks = cpu_to_le64(smm->ll.nr_blocks);
        root_le.nr_allocated = cpu_to_le64(smm->ll.nr_allocated);
        root_le.bitmap_root = cpu_to_le64(smm->ll.bitmap_root);
        root_le.ref_count_root = cpu_to_le64(smm->ll.ref_count_root);

        if (max < sizeof(root_le))
                return -ENOSPC;

        memcpy(where_le, &root_le, sizeof(root_le));

        return 0;
}

static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks);

static struct dm_space_map ops = {
        .destroy = sm_metadata_destroy,
        .extend = sm_metadata_extend,
        .get_nr_blocks = sm_metadata_get_nr_blocks,
        .get_nr_free = sm_metadata_get_nr_free,
        .get_count = sm_metadata_get_count,
        .count_is_more_than_one = sm_metadata_count_is_more_than_one,
        .set_count = sm_metadata_set_count,
        .inc_block = sm_metadata_inc_block,
        .dec_block = sm_metadata_dec_block,
        .new_block = sm_metadata_new_block,
        .commit = sm_metadata_commit,
        .root_size = sm_metadata_root_size,
        .copy_root = sm_metadata_copy_root,
        .register_threshold_callback = sm_metadata_register_threshold_callback
};

/*----------------------------------------------------------------*/

/*
 * When a new space map is created that manages its own space.  We use
 * this tiny bootstrap allocator.
 */
static void sm_bootstrap_destroy(struct dm_space_map *sm)
{
}

static int sm_bootstrap_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
{
        DMERR("bootstrap doesn't support extend");

        return -EINVAL;
}

static int sm_bootstrap_get_nr_blocks(struct dm_space_map *sm, dm_block_t *count)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        return smm->ll.nr_blocks;
}

static int sm_bootstrap_get_nr_free(struct dm_space_map *sm, dm_block_t *count)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        *count = smm->ll.nr_blocks - smm->begin;

        return 0;
}

static int sm_bootstrap_get_count(struct dm_space_map *sm, dm_block_t b,
                                  uint32_t *result)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        return b < smm->begin ? 1 : 0;
}

static int sm_bootstrap_count_is_more_than_one(struct dm_space_map *sm,
                                               dm_block_t b, int *result)
{
        *result = 0;

        return 0;
}

static int sm_bootstrap_set_count(struct dm_space_map *sm, dm_block_t b,
                                  uint32_t count)
{
        DMERR("bootstrap doesn't support set_count");

        return -EINVAL;
}

static int sm_bootstrap_new_block(struct dm_space_map *sm, dm_block_t *b)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        /*
         * We know the entire device is unused.
         */
        if (smm->begin == smm->ll.nr_blocks)
                return -ENOSPC;

        *b = smm->begin++;

        return 0;
}

static int sm_bootstrap_inc_block(struct dm_space_map *sm, dm_block_t b)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        return add_bop(smm, BOP_INC, b);
}

static int sm_bootstrap_dec_block(struct dm_space_map *sm, dm_block_t b)
{
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        return add_bop(smm, BOP_DEC, b);
}

static int sm_bootstrap_commit(struct dm_space_map *sm)
{
        return 0;
}

static int sm_bootstrap_root_size(struct dm_space_map *sm, size_t *result)
{
        DMERR("bootstrap doesn't support root_size");

        return -EINVAL;
}

static int sm_bootstrap_copy_root(struct dm_space_map *sm, void *where,
                                  size_t max)
{
        DMERR("bootstrap doesn't support copy_root");

        return -EINVAL;
}

static struct dm_space_map bootstrap_ops = {
        .destroy = sm_bootstrap_destroy,
        .extend = sm_bootstrap_extend,
        .get_nr_blocks = sm_bootstrap_get_nr_blocks,
        .get_nr_free = sm_bootstrap_get_nr_free,
        .get_count = sm_bootstrap_get_count,
        .count_is_more_than_one = sm_bootstrap_count_is_more_than_one,
        .set_count = sm_bootstrap_set_count,
        .inc_block = sm_bootstrap_inc_block,
        .dec_block = sm_bootstrap_dec_block,
        .new_block = sm_bootstrap_new_block,
        .commit = sm_bootstrap_commit,
        .root_size = sm_bootstrap_root_size,
        .copy_root = sm_bootstrap_copy_root,
        .register_threshold_callback = NULL
};

/*----------------------------------------------------------------*/

static int sm_metadata_extend(struct dm_space_map *sm, dm_block_t extra_blocks)
{
        int r, i;
        enum allocation_event ev;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);
        dm_block_t old_len = smm->ll.nr_blocks;

        /*
         * Flick into a mode where all blocks get allocated in the new area.
         */
        smm->begin = old_len;
        memcpy(sm, &bootstrap_ops, sizeof(*sm));

        /*
         * Extend.
         */
        r = sm_ll_extend(&smm->ll, extra_blocks);
        if (r)
                goto out;

        /*
         * We repeatedly increment then commit until the commit doesn't
         * allocate any new blocks.
         */
        do {
                for (i = old_len; !r && i < smm->begin; i++) {
                        r = sm_ll_inc(&smm->ll, i, &ev);
                        if (r)
                                goto out;
                }
                old_len = smm->begin;

                r = sm_ll_commit(&smm->ll);
                if (r)
                        goto out;

        } while (old_len != smm->begin);

out:
        /*
         * Switch back to normal behaviour.
         */
        memcpy(sm, &ops, sizeof(*sm));
        return r;
}

/*----------------------------------------------------------------*/

struct dm_space_map *dm_sm_metadata_init(void)
{
        struct sm_metadata *smm;

        smm = kmalloc(sizeof(*smm), GFP_KERNEL);
        if (!smm)
                return ERR_PTR(-ENOMEM);

        memcpy(&smm->sm, &ops, sizeof(smm->sm));

        return &smm->sm;
}

int dm_sm_metadata_create(struct dm_space_map *sm,
                          struct dm_transaction_manager *tm,
                          dm_block_t nr_blocks,
                          dm_block_t superblock)
{
        int r;
        dm_block_t i;
        enum allocation_event ev;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        smm->begin = superblock + 1;
        smm->recursion_count = 0;
        smm->allocated_this_transaction = 0;
        brb_init(&smm->uncommitted);
        threshold_init(&smm->threshold);

        memcpy(&smm->sm, &bootstrap_ops, sizeof(smm->sm));

        r = sm_ll_new_metadata(&smm->ll, tm);
        if (r)
                return r;

        if (nr_blocks > DM_SM_METADATA_MAX_BLOCKS)
                nr_blocks = DM_SM_METADATA_MAX_BLOCKS;
        r = sm_ll_extend(&smm->ll, nr_blocks);
        if (r)
                return r;

        memcpy(&smm->sm, &ops, sizeof(smm->sm));

        /*
         * Now we need to update the newly created data structures with the
         * allocated blocks that they were built from.
         */
        for (i = superblock; !r && i < smm->begin; i++)
                r = sm_ll_inc(&smm->ll, i, &ev);

        if (r)
                return r;

        return sm_metadata_commit(sm);
}

int dm_sm_metadata_open(struct dm_space_map *sm,
                        struct dm_transaction_manager *tm,
                        void *root_le, size_t len)
{
        int r;
        struct sm_metadata *smm = container_of(sm, struct sm_metadata, sm);

        r = sm_ll_open_metadata(&smm->ll, tm, root_le, len);
        if (r)
                return r;

        smm->begin = 0;
        smm->recursion_count = 0;
        smm->allocated_this_transaction = 0;
        brb_init(&smm->uncommitted);
        threshold_init(&smm->threshold);

        memcpy(&smm->old_ll, &smm->ll, sizeof(smm->old_ll));
        return 0;
}